In loading or unloading crude oil, liquified natural gas, or other liquified petroleum products, chemicals or the like, between a tanker vessel and shore installations, it is common practice to use special loading arms by which a segmented pipe connection to the shore installation can be maneuvered into position to connect to pipes on the vessel communicating with the tanks. Generally the moving end of the segmented pipe supported by the loading arm is provided with a coupling device which allows the coupler to attach itself to the flanged end of the pipe on the vessel in a manner to form a fluid-tight joint. Preferably this coupler is hydraulically or electrically operated from a remote location. Since the floating vessel may be moving during the coupling operation, or because the coupler must be easily disconnected in an emergency, a quick disconnect coupling system is highly desirable. A number of such couplers have been developed in the prior art, such as shown, for example, in U.S. Pat. Nos. 3,558,161, and 3,865,409. Such couplings typically involve a plurality of clamping assemblies having jaws which are movable in and out of engagement with the flanged end of the pipe on the vessel. These clamping devices are operated by various combinations of linkages and hydraulic actuators which move the jaws in and out of clamping position.
One problem in providing quick disconnect couplers of the type described is that the standard flanged pipe is usually only machined on the end face and the outer edge. The back surface of the flange is generally not machined and therefore the thickness of the flange may vary considerably from pipe to pipe, and in fact the thickness of the flange may vary from point to point on a single flange. The clamping jaws cannot readily accommodate such variations in thickness of the flange. Accordingly it has been the practice to provide an adaptor which is secured to the pipe flange which is machined to close tolerances. The jaws of the coupler then engage the adaptor in clamping the coupler in place on the end of the pipe. However, the use of adaptors is undesirable for a number of reasons, such as the fact they are time consuming to install, they become damaged, lost, or misplaced, and they are a source of added expense. Various coupling designs have been proposed which provide individual adjustment of the jaws to accommodate variations in the thickness of the flange. For example, the jaws have been operated through spring linkage which allows the linkage to yield to variations in the position of the jaws when in the clamping position. Applying clamping pressure through springs, however, may result in insufficient clamping pressure resulting in poor sealing at the coupler. Cam-operated mechanisms have been proposed which provide positive clamping action. However, such systems have involved complex camming arrangements to get a combined radial movement for initially positioning the jaws and axial movement to apply clamping pressure against the back side of the flange.